Dosing Patterns and Economic Burden of Palbociclib Drug Wastage in HR+/HER2- Metastatic Breast Cancer.

INTRODUCTION: Targeted therapies have revolutionized the treatment of hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2-) metastatic breast cancer (mBC). However, as for many oncology drugs, the dose of targeted therapies may need to be adjusted over time, leading to drug wastage when a dose modification is needed but the dose cannot be split or saved. This has been shown to be the case for palbociclib and has led to concerns among payers. This study described palbociclib dosing patterns and estimated the economic burden of the drug wastage associated with palbociclib dose modifications in postmenopausal women with HR+/HER2- mBC. METHODS: A large US claims database was used to identify postmenopausal women with HR+/HER2- mBC who received a palbociclib-based therapy during one of their first three lines of therapy for mBC between February 2015 (palbociclib approval) and December 2015. Dosing patterns (dosing modifications and sequences) were reported; a dose modification was defined as an increase/decrease of at least 25 mg daily compared to the preceding dose. Estimates of drug wastage costs were based on days with overlap in prescription fills for different palbociclib doses. RESULTS: A total of 473 postmenopausal palbociclib-treated women with HR+/HER2- mBC were included (first line 214; second line 157; third line 120). Over an average duration of line of therapy of approximately 4 months, dose modification was observed in 17.8%, 31.2%, and 35.0% of patients in first, second, and third line. Average overlap in prescription fills was 9.2, 9.9, and 5.4 days in first, second, and third line. This potential drug wastage resulted in an average cost of $4376, $4740, and $2592 per patient in first, second, and third line. CONCLUSIONS: This study showed that drug wastage due to palbociclib dose modification results in substantial costs. Treatment options with more flexible dosing may help reduce the costs of drug wastage. FUNDING: Novartis Pharmaceuticals Corporation.